WASHINGTON (Reuters) - A U.S. lawmaker urged the Obama administration to suspend cooperation with a Saudi-led coalition conducting airstrikes in Yemen, saying in a letter released on Wednesday that civilian casualties from the strikes "appear to be the result of war crimes."

Rep. Ted Lieu, a California Democrat, wrote to Secretary of State John Kerry on Tuesday, saying the coalition had conducted more than 70 "unlawful airstrikes" in Yemen.

"It appears that either the Saudi coalition is intentionally targeting civilians or they are not distinguishing between civilians and military targets. Both would be war crimes," wrote Lieu, who had taught classes on the law of war when he was a lawyer in the U.S. Air Force.

His letter increases pressure on the White House over Yemen after the administration announced Saturday it was reviewing support to the Saudi-led coalition after an air strike killed 140 mourners at a funeral.

U.S. arms sales to Riyadh and other support to the coalition should be halted until the White House review is completed, Lieu wrote.

Lieu also cited a Reuters article published on Monday, which reported that the Obama administration went ahead with arms sales to Saudi Arabia despite some officials' fears that Washington could be implicated in war crimes for supporting the Saudi-led air campaign.

The Saudi-led coalition has said it takes its responsibilities under international humanitarian law seriously, and is committed to the protection of civilians in Yemen.

State Department spokesman John Kirby said in a statement on Wednesday: "We have received the letter, and are aware of congressional concerns regarding arms sales to Saudi Arabia. We, too, remain gravely concerned by the high toll of the conflict, including civilian casualties and damage to infrastructure caused by all sides of the conflict."

"Aid and assistance for any country are always under review and subject to modification. We are going to review our position and continue to have further policy discussions," Kirby said.

Several recent efforts in the U.S. Congress to halt arms sales to Saudi Arabia have failed.

But the White House on Saturday announced it was initiating an "immediate review" of U.S. support to the Saudi-led coalition after the apparent coalition air strike on the funeral.

Saudi Arabia has said it will investigate the circumstances of that strike.